Building on the results of four years' cummulative study on several aspects of language-behavior, continued research in a broad cross-cultural and cross-linguistic context is proposed which leads ultimately to an empirically motivated theory of the nature of communicative competence and communicative performance. Topics which represent the major foci of concern include individual projects on the cultural, psychological, and biological bases of human cognition, the social concomitants of language use and language development, and the acquisition of communicative competence and performance skills by the child. BIBLIOGRAPHIC REFERENCES: The Concept of Rank in Ethnobiological Classification: Some Evidence From Aguaruna Folk Botany. Special Issue on Folk Biology. American Ethnologist Vol. 3, #3.